Long-term climate warming and extreme cold events driving ecological
shifts in a deep oligo-mesotrophic lake
Abstract
Deep lakes are critical for freshwater storage, although they are
struggling against major ecological issues from climate change and
nutrient pollution. A comprehensive understanding of internal feedback
mechanisms would be helpful for nutrient regulation within such lakes. A
five-year consecutive study of the diatom community and its abiotic
environment was conducted in Lake Fuxian, which is the largest deep
freshwater lake in China and is currently heading toward a eutrophic
state. The results indicate a shift in the diatom community from a
stable state dominated by a single species to a rapid seasonal
fluctuation, along with a significant increase in diatom biomass.
Specifically, stable stratification and low nutrient concentrations are
limiting the growth of diatom biomass and maintaining the dominance of
Cyclotella. Nutrients in the hypolimnion were replenished in the
epilimnion during the extreme cold of winter, triggering a shift in the
diatom community. This shift may imply that future climate change will
exacerbate the positive feedback of hypoxia-nutrient release of algal
blooms, potentially triggering a regime shift in the ecosystem of the
entire lake. This study underscores the fact that climate change alters
the internal feedback mechanisms of deep lakes and reduces the stability
of their ecosystems, and provides a scientific basis for further
clarification of protection measures for deep lakes.